Size-based passive particle or cell separation and filtration techniques are essential in many environmental and biological applications, including cell separations in cancer therapy, removal of colloidal and supracolloidal residues from wastewater effluents, and filtration of pathogenic bacteria strains such as E. coli O157:H7 from water. Recently, questions have been raised regarding nano- and micro-particle exposure which may have adverse effects on human and animal health. As the use of nanoparticles in manufacturing increases, a growing need to filter particles of nanometer scale from fluids is anticipated. Moreover, in most laboratory-on-a-chip (LOC) applications require continuous on-chip filtration and separation of particles for fast analysis and detection. Conventional micro/nanoparticle filtration systems, including LOCs, traditionally employ membrane-based filtering. The limitations of membrane clogging and pore size make this approach less than optimal and expensive for separating a wide range of particle sizes. This has triggered the recent development of many microscale membrane-free filtration methods for efficient and cost-effective particle filtration, including field-flow fractionation and electrophoresis. However, most of these filtration techniques are active microfluidic systems that require an external force field (e.g., electric field), which often leads to increased design complexity. Thus, developing passive high-throughput filtration methods that offer high filtration efficiency over a wide range of particle or cell shapes and sizes is desired.